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Electric heat certification > electric heat > Flashcards

electric heat Flashcards

1
Q

An example of a resistive load is a:

A

crankcase heater

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2
Q

A GFCI circuit breaker:

A

Detects impedance at appliances.

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3
Q

Voltage imbalance between any legs of a 3-phase power supply may not exceed:

A

2%

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4
Q

The limit switch on an electric furnace is a:

A

automatic reset switch

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5
Q

The sequencer timers on electric heaters will usually energize the 1st heating element after a time delay of:

A

1-30 seconds.

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6
Q

The amount of BTU produced per one watt is:

A

3,413 BTU

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7
Q

60 amps and 230 volts, what is the power?

A

13800 watts

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8
Q

A furnace is using 15,500 watts of power, what is that in kW?

A

15.5 kW

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9
Q

Sequence timers use ________ to close the contact points to the heater element.

A

heated-snap discs or heated bi metal rings

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10
Q

An electric furnace heating thermostat must:

A

Open on a rise close on a drop.

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11
Q

Standard thermostat heat anticipator is _______ and wired in _________ with the heating control.

A

adjustable/ series

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12
Q

Some thermostat manufacturers require a jumper connection on the thermostat sub-base of heating and cooling thermostats in order to:

A

use a single transformer.

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13
Q

Most electric heat elements use the following safeties to prevent overheating.

A

Snap-disc and fusible link.

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14
Q

70 amps and 230 volts, what is the BTUs?

A

Find wattage P=IV 16,100 x 3.413 = 54,949

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15
Q

The control that prevents duct heaters from operating unless there is adequate supply air is:

A

fan interlock.

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16
Q

The coefficient of performance for electric resistance is:

A

1 to 1

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17
Q

What is the maximum kW element used on each contact of a residential heat sequencer?

A

5 kW

18
Q

Electric heaters are generally rated at _______ volts AC for kW output.

A

240

19
Q

An automatic reset safety switch in a heating element generally opens at _______ F

A

130-190

20
Q

The first stage of a sequence timer usually has a set of contacts to:

A

start the blower fan motor.

21
Q

Most heating elements are mounted on which type of insulators?

A

Mica or ceramic

22
Q

What will a 10 kW heater wired to 480 volts draw in amps?

A

21 amps

23
Q

The purpose of a sequencer is to:

A

avoid a sudden power overload.

24
Q

Two major factors in determining the temperature rise of an electric furnace are:

A

Furnace kW and CFM

25
Q

A major cause of electrical heat element burnout is:

A

low airflow.

26
Q

A technician is checking resistance on a delta three phase motor. If one element is open, he would read:

A

He would read that between L1- L2-L3 there is ONE reading of infinity ohm.s.

27
Q

The purpose of setting a heat sequencer anticipator properly is:

A

control cycling time.

28
Q

10 kw heater installed in a 2 ton system should have a flow of _____ CFM

A

300-500

29
Q

Resistance to air flow (static pressure) is measured in an electric heater in:

A

inches of water column

30
Q

To properly set a heat anticipator, the technician should measure amps between terminals _________ on thermostat sub-base.

A

R-W

31
Q

If a technician installs a 15 kW electric furnace on a 3 ton system, there should be how many thermostat conductors?

A
  1. R,B,W,Y,G
32
Q

To measure grill air speed, the tech should use a:

A

anemometer.

33
Q

a 1/3 single phase PSC electric blower would draw approx. _________ at 240 volts AC

A

2-4 Amps

34
Q

On a delta phase motor L1- L2 11 ohms
L1 - L3 22 ohms
L2 - L3 11 ohms whats wrong?

A

L1 -L3 is shorted

35
Q

a 1200 CFM furnace operating with a 10 kW heater at 240 volt AC would have a temperature rise of _____________ F

A

20-30

36
Q

In a heat pump, the heating element is controlled by what stage of the thermostat?

A

Auxiliary heating.

37
Q

Typical RPM of a residential direct driven blower is:

A

1,000 - 1,200 RPM

38
Q

The drive belt width used on fractional HP motors is:

A

A

39
Q

Most residential air conditioning and electric heating systems will have a fan system rated for a maximum total pressure loss of:

A

0.02 - 0.1 inches of WC

40
Q

Turning vanes are added to the sheet metal elbows to:

A

increase air velocity.

41
Q

The MAX recommended return air velocity of a residential filter grill is:

A

400 fpm

Electric heat certification (1 decks)

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